Molly Ball at The Atlantic writes The One Number That Will Decide This Year's Election: What will be the deciding factor in this year's elections? Will it be Obamacare? The chaos erupting across the globe? The president's approval rating? Will it besingle women voters, Hispanics, young people? Mike Podhorzer crunched the numbers and found there's one factor that, with eerie consistency, explains the way elections have swung for the past decade.